OBJECTIVETo explore the intervention of Fagopyrum cymosum (Trev.) Meisn alcohol extract (FAE) on defecation function and motor functions of isolated colons of diarrhea-predominant irritable bowel syndrome (D-IBS) rats and to study its underlying mechanism.

METHODSThe D-IBS rat model was established by neonatal pups maternal separation (NMS) combined with intracolonic infusion of acetic acid (AA). Adult IBS rats were randomly divided into the pre-intervention control group (n = 10, with no gastrogavage), the normal saline control group (n = 10, administered with normal saline by gastrogavage), the pre-treatment model group (n = 8,with no gastrogavage),the normal saline model group (n = 8, administered with normal saline by gastrogavage), the low dose FAE group (n = 8, administered with 6 g/kg FAE by gastrogavage), the high dose FAE group (n = 8, administered with 24 g/kg FAE by gastrogavage), and the Pinaverium Bromide group (n = 8, administered with 0.02 g/kg Pinaverium Bromide by gastrogavage). All medication was performed once daily for 2 weeks. The abdominal withdrawal reflex (AWR) was employed to evaluate the visceral hypersensitivity; their loose and watery stool grade was assessed by Bristol scores for stool consistency; and their fresh feces weight was calculated. In vitro effect of different concentrations of FAE and Pinaverium Bromide (0.02 μg/mL) on spontaneous contraction and spasmodic contraction induced by acetylcholine (Ach) in rats' isolated colon were observed and the influence on the intestinal calcium channel was evaluated.

RESULTSCompared with the pre-intervention control group, the pain pressure threshold and the maximum tolerance pressure decreased significantly in the pre-intervention model group (P < 0.05), and the loose and watery stool grade and fresh feces weight increased drastically (P < 0.01). Compared with the normal saline control group, the pain pressure threshold and the maximum tolerance pressure decreased significantly in the normal saline model group (P < 0.05), and the loose and watery stool grade and fresh feces weight increased markedly (P < 0.01). Compared with the normal saline model group, the pain pressure threshold of 24 g/kg FAE and Pinaverium Bromide group significantly increased (P < 0.05). The loose and watery stool grade and fresh feces weight decreased obviously in the low dose FAE group, the high dose FAE group, and the Pinaverium Bromide group (P < 0.05). FAE (30, 100, 300, 1,000, and 3,000 μg/mL) and Pinaverium Bromide could significantly inhibit spontaneous contraction of isolated intestines (P < 0.05, P < 0.01), and FAE (30, 100, and 300 x 10(-6) g/mL) could remarkably inhibit their spasmodic contraction and contractile tension induced by Ach and Ca2+ respectively (P < 0.05, P < 0.01) in a concentration-dependent manner. Pinaverium Bromide also could significantly inhibit Ach and Ca2+ induced contraction.

CONCLUSIONEffective components of FAE improved the defecation function and inhibited enterospasm induced intestinal hyperactivity in IBS model rats via antagonizing calcium channel competitively and inhibiting colonic motility dose-dependently.